Fluids produced from oil wells penetrating an oil-bearing formation primarily include crude oil and water and are herein referred to as formation fluids. A formation fluid may also contain natural gas and natural gas condensate which may or may not be desirable and may be the primary product of a given well in which case the well is referred to as a gas/gas condensate well. A formation fluid may also contain CO2 and insoluble clay and silica particles from the reservoir. Contained within the formation fluids are components that under certain conditions can precipitate and impede the production of oil and gas. These components include paraffins and asphaltenes from crude oils and gas condensates and inorganic mineral scales from formation water.
It is known in the art of oil and gas production to eliminate or mitigate the effects of undesirable paraffin, asphaltene, and scale precipitation. For example, to aid oil and gas production, many chemicals, referred herein as “additives”, which include paraffin inhibitors, asphaltene inhibitors, scale inhibitors, and the like, are often injected from a surface source into wells or flowlines to treat the formation fluids flowing through such wells and flowlines to prevent or control the effects of precipitation of paraffins, asphaltenes, and mineral scale.
These additives can be injected continuously or by batches into wellbores, at wellheads, or other locations in flowlines or pipelines carrying formation fluids. In addition, an additive can be injected into a near wellbore formation via a technique commonly referred to as “squeeze” treatment, from which the additive can be slowly released into the formation fluid. Injection of additives upstream of the problem location is preferred. Sometimes, additives are introduced in connection with electrical submersible pumps, as shown for example in U.S. Pat. No. 4,582,131, or through an auxiliary line associated with a cable used with the electrical submersible pump, such as shown in U.S. Pat. No. 5,528,824. In addition, in wells without a packer in the completion, additives may be applied via pump or truck into the annular space between the tubing and the casing with a fluid flush driving the additive into the formation fluids.
Of the additives that can be added to formation fluid from oil and gas wells, the paraffin inhibitors are especially important. U.S. Pat. No. 4,110,283 to Capelle discloses that a copolymer of 4-vinyl pyridine and acrylic acid esters dispersed in an aqueous medium can prevent the deposit of solid paraffins on the walls of containers and pipelines carrying oil. U.S. Pat. No. 6,218,490 to Brunelli, et al., discloses that alcohol acrylate copolymers combined with 2- and 4-vinyl pyridine and acrylic acid esters can be used to prevent the formation of paraffin deposits. U.S. Pat. No. 3,951,161 to Rohrback, et al., discloses a method of using electrical contact resistance to detect the formation of paraffin solids in oil and gas wells. U.S. Pat. No. 4,538,682 to McManus, et al., discloses a method for removing paraffin deposits. All of these patents illustrate the need to control the formation of paraffin deposits.
Paraffin inhibitor additives are typically applied in the form of organic solutions or aqueous microemulsions or admixtures. The use of liquid additives is not without problems. At cold temperatures, such as in cold weather or deepwater subsea locations, the additives may freeze or gel during transportation or use. Supplying a source of heat, particularly for deepwater and remote well sites can be a problem. Also, when supplying additives in the form of liquids, the solid active components must be co-shipped in solution. The use of a solvent to form the solution requires that inert or non-active components must be co-shipped with the active components.
It would be desirable in the art of oil and gas production to use paraffin inhibitor compositions that have a higher concentration of active components than conventional paraffin inhibitors. It would be particularly desirable to use such compositions that allow for higher active component concentrations under cold temperatures.